Scholarly literature claims that health declines in populations when optimism about investing in the future wanes. This claim leads us to describe collective optimism as a predictor of selection in utero. Based on the literature, we argue that the incidence of suicide gauges collective optimism in a population and therefore willingness to invest in the future. Using monthly data from Sweden for the years 1973–2016, we test the hypothesis that the incidence of suicide among women of child-bearing age correlates inversely with male twin births, an indicator of biological investment in high-risk gestations. We find that, as predicted by our theory, the incidence of suicide at month t varies inversely with the ratio of twin to singleton male births at month t + 3. Our results illustrate the likely sensitivity of selection in utero to change in the social environment and so the potential for viewing collective optimism as a component of public health infrastructure.

中文翻译：

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对子宫内男性双胞胎的集体乐观和选择

学术文献声称，当对未来投资的乐观情绪减弱时，人口的健康状况会下降。这一主张使我们将集体乐观描述为子宫内选择的预测因子。根据文献，我们认为自杀的发生率衡量了人群中的集体乐观情绪，从而衡量了对未来的投资意愿。我们使用瑞典 1973 年至 2016 年的月度数据，检验育龄妇女的自杀率与男性双胞胎出生率成反比的假设，而男性双胞胎是高危妊娠生物投资的指标。我们发现，正如我们的理论所预测的那样，每月的自杀发生率吨与当月双胞胎与单胎男婴的比例成反比吨+ 3. 我们的结果说明了子宫内选择对社会环境变化的可能敏感性，因此有可能将集体乐观视为公共卫生基础设施的组成部分。